EARTH CHANGES AND EVOLUTION 195 



o 



zontal strata occurring in similar beds for thousands of feet 

 thick, while each successive bed must have been formed at or 

 near the surface. Such are the deposits recently formed in the 

 deltas of great rivers, in many of which borings have been 

 made from 350 to 640 feet deep, with indications that each 

 successive layer was formed near the surface, and that during 

 the entire process of deposition the whole area must have been 

 sinking at a very regular rate. This can best be explained 

 by the weight of the matter deposited causing the slow sub- 

 sidence. Exactly similar phenomena occur through the whole 

 series of the geological formations to the most ancient ; in some 

 cases strata eight miles in thicloiess showing proofs that the 

 very lowest beds w^ere not deposited in a deep ocean, but in 

 quite shallow w^ater near shore. ^ 



Now, as w-e have seen that, over many areas not far from 

 shore, deposition may occur 100 or even 1000 times as fast 

 as denudation, and that this same area is continuously lowered 

 by the weight forcing the crust downwards, we have a real 

 and efficient cause for continuous subsidence and the forma- 

 tion of parallel strata of enormous thicknesses. It remains to 

 account for the subsequent upheaval of these areas, their tilt- 

 ing up at various angles, and in many cases their being frac- 

 tured, curved, or contorted often to an enormous extent and 

 in a most fantastic manner. 



Effects of a Cooling and Contracting Earth 



It is universally admitted that the earth is a cooling and 

 therefore a contracting body. The cooling, however, does not 

 take place by conduction from the heated interior through the 

 solid crust, the temperature of which at and near the surface 

 is due wholly to sun-heat, but by the escape of heated matter 

 to the surface through innumerable hot or warm springs; by a 

 continuous flow of heated gases from volcanic areas; and fre- 

 quent outbursts of red-hot ashes or liquid lavas from vol- 



1 In chapter iii. of vol. i. of my Studies Scientific and Social I have given 

 details of these phenomena on the highest geological authority. 



